The objectives of this project are to investigate the factors that differentially regulate the storage, synthesis, and secretion of the gonadotropins, LH and FSH. Five interrelated specific aims are proposed. The first is to discover the site of delay in LH rise in female rats in response to removal of gonadal negative feedback. In vitro tests of hypothalami in a perifusion culture system will be used to determine whether there is a sex difference in GnRH secretion post-gonadectomy. The second aim is to examine pituitary, gonadal, and adrenal factors which regulate inhibin synthesis and secretion. The third aim is to discover the role of progesterone feedback on differential LH/FSH secretion using the progesterone receptor antagonist RU486. The fourth aim is to study the site of glucocorticoid differential regulation of LH and FSH synthesis and secretion. An ectopic pituitary transplant model will be used to examine whether the pituitary is the site of suppression by glucocorticoids of the response of LH to GnRH. The fifth aim is to investigate the site of action of hyperprolactinemia in the preferential suppression of LH over FSH secretion.